Motor-control system



8 19, 1930- B. w. JONES 1,773,623

8010!! CONTROL SYSTEM Filed May 14, 1925 off l 0 pecan J 4 11am?Qi-ncczz 4/ N I v =9 I ralrwar J Inventor Benjamin w. Jones,- b5 W J HisAttorney Patented Aug. 19, 1930 UNITED STATES PATENT OFFICE BENJAMIN W.JONES, OF SCHENECTADY. NEW YORK, A SSIGNOR TO GENERAL ELECTRIC COMPANY,A CORPORATION OF NE\V YORK MOTOR-CONTROL SYSTEM Application filed- May14,

My invention relates to improvements in systems of motor control wherebya speed variation of the motor may be ell'ected on a time basis whileconditions are suitable and 5 the rate of speed variation may beautomatically limited to take care of the conditions in which the speedvariation etiected by the means acting on a time basis is not suitable.

Although not necessarily limited thereto, the invention is particularlyapplicable to the control of an electric motor operating an elevator soas to prevent an excessive rate of acceleration. If a motor isaccelerated from rest to full speed in a lixed time and maintains thesame rate throughout then the rate of the motor speedacceleration islixed The rate will vary as the time is varied. However, due to theoverhauling action and the positive load action of elevators a uniformrate of operation of speed varying means does not result in a uniformrate of change of motor speed. If the rate is as high as can be allowedunder one condition, then it will not be suitable for other conditions.

In accordance with my invention, the speed variation of the motor isordinarly eli'ected on a time basis and the action of the means actingon the time basis is automatically modified so as to take into accountthe variations in theconditions encountered which make a straight timeelement control unsuitable.

In carrying the invention into eli'ect in a manner to explain theprinciples thereof, I

rovide speed varying means normally actlng on a uniform time basis andautomatically retard the action of said timing means in response to therate of speed variation effected thereby. Thus, the acceleration of themotor normally proceeds on a time basis and too rapid acceleration isprevented in cases where the time basis accelcratirm would notfunctionto produce the desired results.

For a more complete understamline of my invention, reference should behad to the accompanying drawing, the single figure of which illustratesin diagraimnatic form a system of control embodyingmy invention.

In the system illustrated in the accompany- 1926. Serial No. 109,127.

in; drawing. the means for obtaining speed variation of the controlledmotor taltes the form of a pilot motor operated switch for governingresistor controlling contactors and the means for modifying: orarresting the action of the timing means takes the form of a normallyclosed electromagnetic switch having a winding thereon connected acrossthe armature terminals of the motor so as to be energized in uccordamrewith the counter cleclroinotive force of the motor. This switch is ofthe type which is constructed and arranged so as to automatically openits contacts responsivelv to the rate of change of the encrgization ofsaid winding. iv this means, theatcclcration ot' the controlled motorproceeds on a time basis while the condi tions are right for timecontrol and in case the acceleration cll'ected thereby is too rapid, theelectronmanctic switch will dcencrgize the pilot motor and therebytemporarily arrest further action thereof until the rate of change ofthe motor speed has decreased.

A more detailed explanation of the system disclosed in theact-onipairving drawing will now be given. The electric motor having anarmature l0 and a shunt licld 11 is arranged to drive any suitable load.as for example. an elevator. The resistor having aplurality oi sections12. 1; 11 and .15 is included in series relation in the circuit ofarnmture 10. The contactors 1o. l7. l8 and 19 are provided for shuntingthe resistor sections 12. 13, H and 1.3, respectively. A resistorhavinga plurality of sections 20, 21 and 22 is included in shunt relation withthe arnzature il The normally closed contactors 23, 21 and 25 areprovided for controlling the resistor sections in. 21. :2. respectively.so as to vary the value of current shunted from the armature 10. Thevarious resistor ((lllltlt'lt l. are controlled by means of the pilotmotor operated switch Qt; which is provided with a rotatable switchmember 27 arranged to make engagcnicnl with the segments 28 so as toenergize the resistor contai'lors in a dclinitc succession. The switcharm :37 is operated by mean of the reversible pilot motor 29 which isprovided with a split ticld winding, the portion ill) of which isprovided for operation of the pilot motor in a direction to ell'cctacceleration ol' the main driving motor and the portion ll of which iprovided for ellccting a return of the switch arm '37 to the ol't'position. that indicated in the drawing. The pilot notor git operates ata substantially constant speed. The pilot motor operated rheostat actingthrough the various resistor t0Ill2l"l I and the resistor sectionscontrolled thereby. provides a means for ellcctllig speed regulation ofthe main driving motor on a detinite time basis.

As before referred to. this speed variation on a time basis may not besuita le for all of the conditions encountered and to talte care ofconditions in which the speed ariation ctl'ccted by the means operatingon a time basis proceeds at too rapid a rate. 1. have provided thenormally closed electromagnetic switch 2):. which has its principalwinding 2525 connected 2lCl'U S the terminals of the armature lU ot' themain driving motor. This switch is indicated as of the type disclosed inmy Lnited States: .latent Xo. l,TtJ3,lo' 3, l ebrnarv :t', 1039. whichis assigned to the same assignec as this application. The magneticstructure of the switch is of E shaped form, with the winding Ildisposed on the middle leg thereof. A short circnited winding Ill isdisposed on the upper leg of the magnetic structure and the magneticmember or armature -35 is pivotally mounted adjacent the middle leg onwhich the principal winding 33 is mounted. The armature 55.") carries atits upper end a contact 3t which is arranged to make engagement with thestationary contact HT, and these ontacts are normally held in engagementby means of the biasing spring 115 acting on the lower end of thearmature 235.

in general. the operation of the switch 32 is as to lows. While theenergization of the winding I33 is a substantially constant value, theflux up thereby in the E shaped magnetic structure will distributebetween the two parallel paths in such a way that the armature 35 willremain in its biased position. One of these paths is through the middleand upper legs of the magnetic structure and the other of the paths isthrough the middle and the lower legs of the magnetic structure. Thesemagnetic two parallel paths will be so nearly in balance that thebiasing eti'ect ot the spring 3b will maintain the contacts 36 and inengagement while the energization ol winding 33 is a substantiallvconstant value. However, it' the energization of the winding 33 isincreased at a rapid rate. as will be the case if the acceleration ofthe main driving motor is relatively rapid. and the rate of increase ofthe counter electroinotivc force of the main driving motor iscorrespondingly high. the liux distribution in the two paths of themagnetic structure of the switch will be changed. the flux through thelower path predominating over the flux e rotate in a clockwisedirection.

through the upper path. This is because of the fact that theshort-circuited winding 3i on the upper leg of the E shaped magneticstructure etl'ects a retarding action on the building up of the lluxthrough the upper of the two magnetic paths. The lower end of thearmature {)5 will then be attracted to the lower end of the E shapedmagnetic structure of the switch against the biasing action of thespring 23o. thereby opening the contacts 36 and 3? and deenergizing thepilot motor 29 so as to arrest temporarily further action of the timingmeans.

is thu constructed and arranged and with the parts in their respectiveposition indicated in the drawing. it will be assumed that it is desiredto connect the main driving motor to the source of supply 5t) andaccelerate the motor from rest to the full operating speed in accordancewith the invention. The handle 4U oi the master switch will be rotatedclockwi e into its lirst delinite position, thereby energizing thedirection contactor it and connecting the motor to the source of supplywith the resistor sections 1), l3. 1i and 15 included in series relationwith the motor armature and the resistor section 20 included in shunt tothe moto armature 10. in order to ell'ect l'urther speed acceleration ofthe motor, the handle at) will he moved further in a clockwisedirection, thereby energizing the pilot motor 525) through a circuitincluding the limit switch 42. the switch contacts 236 and 37, the fieldwinding 30 and the pilot motor armature to the source of supply. Thepilot motor will now rotate at a substantially constant speed in such adirection that the switch arm 27 will be caused to This clockwiserotation of the switch arm '27 cliected by the pilot motor will proceedon a definite time basis so as to accelerate the main driving niotor.The contactor 19 will be first energized to shunt the resistor section15, then the contaetor 25 will be energized to open and include theresistor section 22 in shunt relation with the armature 10, thecont-actor 18 will then be energized to shunt the series resistorsection 14-. the contactor it will then he energized to open the shuntaround the armature shunting resistor section 21. next the cont-actor 17will he energized to shunt the series resistor section 13, then thecontactor J3 will be energized to open and thereby Open the circuitthrough the shunting resistors 20. 21 and Q2, and linally the contactorit) will he energized to shunt the series resistor section 12.

If the rate of acceleration etiect'ed through the operation ol the pilotmotor 2!) operating on a time basis is at any time too high, the rate ofincrease of the counter electromotive l'orce ot' the motor will hecorrespondiugly high and the switch 21; will thus be. caused to operatein the manner previously explained so as to open'the contacts 36 and 3?and thereliy arrest temporarily the action of the pilot motor 2%). Whenthe rate of increase of the counter elta-troimitive force of the motor,and thus the rate of acceleration of the motor, has dcm'eased. thecontacts of the switch 32 will he returned to their closed positions andthe pilot motor automaticall reenergized to connone the acceleration ofthe main controlled motor on a time basis. \Yhen the switch arm :5? ofthe pilot motor operated ontrollenis in the full running" 1)t) lll()llthe limit switch l2 will be opened therein opening the circuit of thearmature and tield winding 3t) of the motor 2! and further a tion of thepilot mo tor in this direction will be arrested.

When the handle it) of the master switch is returned to the oll'position. the pilot motor is automatically energized from the source ofuppl through the limit switch 43 and the tield winding Ill so as toautomati ally return the switch arm 27 to the position indicated in thedrawing. \Vhen the handle 40 of the iztaster switch is then turned inthe counter lockwise d rection to ell'ect reverse operation of the maindriving motor, the directional coutactor it will this time be.energrized and the main driving motor will be accelerated in the reversedirection on a time basis. moditied by the switch 32 in accordance withthe rate of speed variation, in a manner similar to that above explainedin connection with the a celeration of the main driving motor in theforward direction.

In accordance with provisions of the patent statutes. 1 have describedthe principle of operation of mv invention. together with the apparatuswhich I now consider to represent the best embodiment thereof. but Idesire to have it understood that the apparatus shown is onl villustrative and thatthe invention ean be arried out by other means.

What I claim as new and desire to secure by Letters Patent of the UnitedStates is as follows:

1. A motor control system. comprising a motor, speed controlling meanstherefor cornprising a resistor in the motor circuit, means including: apilot motor for varying the said resistor on a time 1 isis, and anelectromagnetic switch having a winding connected across the armatureterminals of said motor and a magnetic movable member operated therebyin accordance with the rate of change of the counter electromotivevt'orce of the motor for ileenero'iZinc said pilot motor to limit therate of speed variation of the motor.

A motor control system comprising a motor. a resistor in the circuit ofsaid motor, a pilot motor for varying said resistor on a time bases. andmeans operated responsively to the rate of change of thectntntenelectromotive i'oree of said motor for dcenergizing said pilotmotor to limit the rate of speed variation of said motor.

25. A motor control system comprising a motor, speed controlling meanstherefor comprising a resistor included in series relation in thearmature circuit of said motor and a resistor included in shunt relationwith the armature circuit of said motor, means including a pilot motorforvarying said resistors on a time basis, and an clectro-magneticswitch having a winding connected across the armature terminals of saidmotor and a mag netic movable member operated thereby in accordance withthe rate of change of the counter-electromotive force of said motor foropening; the operating circuit of said pilot; motor to limit the rate ofspeed variation of said i'notor.

In witness whereof, I have hereto set my hand this 12th day of May,1926.

BENJAMIN \V. JONES.

